"We think we are in the extra innings, perhaps the 11th inning, of a 14-inning ballgame when it comes to the auto cycle. We are at a point where you have to make it worth someone's while to get into a dealership," Jonas, head of global auto research for Morgan Stanley, told CNBC's "Power Lunch" on Thursday.
The industry is already ramping up incentives, with Ford's up 20 percent in July.
Jonas believes Ford may be exposed to some of the pressures on the car market, because it made a big effort to reposition itself to smaller models that might be more successful at higher oil prices.
Michelle Krebs, director of automotive relations at AutoTrader.com, also thinks the industry is reaching its peak.
"We actually thought that the peak should have been earlier. We have been warning about this for quite some time," she told "Power Lunch."
AutoTrader's forecast is for auto sales for July to be down 2 percent.
"We've always said that this year will … maybe eek out another record, but possibly not. As the year has progressed, we thought probably not," she said.
She said vehicle affordability is a huge factor — with the price of everything going up, except wages.
There has also been a huge shift toward trucks and car-based sports-utility vehicles, she said.
For Jonas, that's good news. He thinks the move can enhance the profits and market valuation of Fiat Chrysler, one of his top picks.
"We think that the management team understands the sense of urgency that the industry is facing, both in terms of where we are in the cycle and the technological disruption that is, let's say, transforming the industry from a business that is selling cars to one that is selling miles, time and experiences."
— CNBC's Phil LeBeau and Gina Siniscalchi contributed to this report.
Disclosures: Fiat Chrysler FCAU is an investment banking client of Morgan Stanley. Morgan Stanley & Co. LLC makes a market in the securities of Fiat Chrysler Automobiles. Morgan Stanley & Co. International PLC and its affiliates have a significant financial interest in the debt securities of Fiat Chrysler. Within the last 12 months, Morgan Stanley has received compensation for products and services other than investment banking services from Fiat Chrysler. Ford Motor is an investment banking client of Morgan Stanley. Within the last 12 months, Morgan Stanley managed or co-managed a public offering of Ford Motor Company.